Curb boxes are widely employed to provide access to buried utility service and distribution lines such as gas and water systems, and many curb boxes are formed of a pair of synthetic plastic components frictionally telescoped with respect to the vertical dimension for accommodation to the depth of the service or distribution line and protection against damage to the lines upon a vertical force being applied to the curb box cover. An example of such a curb box, and the method of forming the same, is shown in the assignee's U.S. Pat. No. 3,548,864.
When installing a curb box, an open trench exists in which the conduit and associated valve is laid. The curb box is placed over the valve, and the trench is back filled. During the back filling procedure it is important that the curb box remain properly located with respect to the valve, and even though the back filling may be by bulldozers, back hoes or other power equipment, the curb box must stay positioned on the valve even though subjected to lateral forces and pressures while being covered. Bases have been employed with curb boxes as disclosed in the above identified patent, and as it is desired that the curb box protect the valve from vertical forces imposed upon the curb box it is desirable that the vertical support of the curb box be sufficient to prevent such vertical forces from being directly imposed on the valve so that telescoping of the curb box components may take place prior to damaging the valve and conduit system.
Synthetic plastic curb boxes are known which are of the "snap-on" type whereby the curb box may be frictionally positioned on the conduit system by a vertical downward force. In such constructions the resilient nature of the bell housing material permits portions of the curb box bell housing to be forced outwardly as the bell housing is forced over the pipe through a restricted dimension, and such constructions permit the curb box to be readily positioned on the subterranean pipe system. However, as such prior art "snap-on" curb box constructions engage the cylindrical pipe their resistance to rotation or tilting relative to the conduit system is minimal even though such prior devices do provide adequate resistance to vertical movement. Examples of such prior art devices are shown in U.S. Pat. Nos. 3,601,143 and 4,030,519. As such prior devices engage the circular configuration of the pipe little resistance to rotation of the curb box about the axis of the pipe is presented, and it is necessary for an operator to hold the curb box a vertical orientation during back filling to insure the proper curb box final position while being covered.
It is an object of the invention to provide a service line curb box of synthetic material which frictionally engages a valve housing adjacent the valve operator at a non-circular cross sectional portion of the conduit system wherein such frictional engagement resists vertical displacement of the curb box relative to the valve, and simultaneously resists rotational curb box rotation about the axis of the valve associated therewith.
It is an additional object of the invention to provide a synthetic plastic curb box having a bell housing which frictionally grips the sides of a valve housing, may be readily placed upon the valve by a vertical downward movement, and wherein the configuration of the bell housing engages the earth adjacent the valve such that downward vertical forces are resisted by the housing and not imposed upon the valve.
A further object of the invention is to provide a synthetic material curb box which includes relatively complex configurations, yet be economically produced by inexpensive molding techniques.
In the practice of the invention a synthetic plastic curb box lower portion includes a cylindrical upper portion for telescopingly receiving the upper curb box portion and a lower bell housing adapted to receive a subterranean conduit system valve. The housing includes arched openings intersecting the open lower end whereby the pipe associated with the valve enters the housing. The opposite sides of the bell housing are provided with inwardly extending projections of similar configuration opposed to each other, and including valve engaging surfaces which, normally, are spaced apart a distance slightly less than the dimension of the valve surfaces which they engage. Also, the housing projections include obliquely oriented cam surfaces defined upon bosses which aid in opening the bell housing to receive the valve, and provide additional frictional resistance to removal of the curb box from the valve.
The curb box is installed by forcing the curb box over the valve causing the bell housing to open or spread, and as surfaces defined upon the projections frictionally engage the valve at a non-circular transverse cross sectional location relative rotation of the curb box and valve is resisted.
The projections are formed in such a manner on the bell housing that surfaces thereof will engage the earth adjacent the valve for supporting the curb box, and directly transmitting vertical forces imposed upon the curb box to the earth, rather than upon the valve or conduit system.